A226436 Number of permutations of {1..n} with fewer than 3 interior elements having values lying between the values of their neighbors.

1, 1, 2, 6, 24, 118, 658, 4078, 27724, 205134, 1641534, 14132390, 130299584, 1281352790, 13391026730, 148237230942, 1733059331604, 21341010960286, 276120222880246, 3745333514843734, 53149568086851784, 787599172764342822, 12166057777073762082

Offset

0,3

Links

Alois P. Heinz, Table of n, a(n) for n = 0..483 (terms n = 1..210 from R. H. Hardin)

Example

Some solutions for n=9
..6....4....3....9....7....7....9....5....8....8....1....8....8....7....6....2
..1....2....2....2....3....4....3....3....1....4....4....3....4....1....4....1
..3....8....8....1....2....8....4....9....9....3....3....9....2....2....8....7
..9....3....7....6....8....3....2....1....4....7....5....5....9....6....5....9
..5....7....5....5....5....5....5....8....6....6....2....7....1....3....9....3
..2....9....6....3....1....9....7....2....7....2....8....4....5....5....2....6
..8....1....4....7....6....1....6....7....3....9....9....6....3....8....3....4
..4....5....9....4....4....6....1....4....5....1....7....2....6....4....1....5
..7....6....1....8....9....2....8....6....2....5....6....1....7....9....7....8

Crossrefs

Column 3 of A226441.

Sequence in context: A319027 A228397 A164871 * A224318 A079106 A247472

Adjacent sequences: A226433 A226434 A226435 * A226437 A226438 A226439

Keyword

nonn

Author

R. H. Hardin, Jun 06 2013

Extensions

a(0)=1 prepended by Alois P. Heinz, Jul 17 2024

Status

approved